Reaction blading



Octa 2o,`1931. B. v. DENSMORE 1,828,409-

REACTION BLADING Filed Jan. ll, 1.929

F l 14 Y WITNESS 5 INVENTOR 6&1". BMDensmm-e a v l' Bf GMP3] ATTORNEYPatented Oct. ZO, 1931 BENJAMIN V. DENSMORE, OF RIDLEY PARK HOUSEELECTRIC av MANUFACTURING CoMPANYyA vco aioitlirrloiv oF rrnivlvsvr.`

REACTToNjTlAnINe Application filed January 11,1929.' Serial. k111'0.

' VANIA 'j My invention relates to elastic fluid turbines, and moreparticularly to the reaction blading for such turbines, and it has foran object to improve the efficiency of apparatus of this character.

It is one of the inherent characteristics of reaction turbines, or ofthe reaction stages of any turbine, that the pressures on the oppositesides of each row of blades are different. This is due to the fact thatthe steam expands in the moving as well as in the stationary blades andthere is a drop in pressure between the two sides of every row ofblades. Hence, there is a tendency for steam, or other working fluid topass ina Continuous stream around the tips of the blades toward theregion of lower pressure.

To counteract this tendency, it is customary to provide a relativelysmall clearance between the tips of the moving blades and the casing, inone instance, and between the tips of the stationary blades and therotor, in the other. Under such conditions, rubbing sometimes occurs atthe tips'of the blades, causing the latter to chatter, or vibrate. Thenthis rubbing occurs, thetip of ai blade is temporarily retarded soV thatthe blade is bent backwardly until it is free of the rubbing surface, oruntil its resiliency causes it to snap forward and thus, to thrust itstip portion directly toward, or into any adjacent, or rubbing surface,andthe blade is. again bent backwardly, and so on; themotions justdescribed being those which occur when the blade is in a vibratorycondition. Y

The more serious consequences are due to impacts, or-other Contactsresulting from the forward swing of the tip ofthe blade and which causethe rubbing surface to seize the tip, or to otherwise arrest thisforward Inotion, for such contacts tend. to push the tip of a bladedirectly into any adjacent surface. It will be apparent, therefore, thata relatively slight rubbing at the tip of a blade may easily Causesuicient chattering, or vibration, to eventually produce a failure bybreakage. Y- Y It isa more particular object of this invention,therefore, to provide turbine blades with 'means for Vrubbing occurs.

`preventingserious vibration when l This and otherobjects areeflected bymy invention, aswill vbe lowing vdescription and claims taken inconnection with the accompanying drawings,

wherein Figflis an elevation of a'reaction blade; 'and f Fig. 2 is afragmentary sectional view of a turbinehavlng blades y,1n accordancewlththe present invention)` Accordingto one preferred formofinyVinvention, thetip of a reaction blade'is proyvided with a Abendableextension. whichis formed as continuation'ofa working surface ofthefblade, and inclinedbaclawardly with respect to "thefdir'ection ofrotation. jyfvir` tue of this backwardly inclined extension, it

isassured that,should any rubbing occur, fthe'eizte'nded portionwillme'rely be bent over, the point Iof contact will 'always follow theblade and the tip portion Vwillnot be pushed directly'but.willdrag'overitin such amanner as to `destructive vibration.

y.tend to dampen vibration, thus 'avoiding any This'will be'moreapparent from the draw"- sisting of ablade portionl, as usual, and arelatively'thin, 'extension l2. As

.showninfFig 2, theblade is :mounted on a turbine rotorl', the tip endof the blade portion 1l being disposed, adjacent the casr apparent from1the foltoward, or intothe rubbing surface, j

ingswher'ein I have shown theblade 10, conpreferably as a continuationof the face of the blade, and thisl extension is also initially inclinedbackwardly with lrespect to the direction of rotation, or with respectto the direction of relative the blade and any tip might come in rubbingContact. A close radial sealing clearance, indicated at`15`, is providedbetween the bendable extension 12 vand the adjacent surface of thecasing'll, so

that the bendable extension is normally not in contact with saidsurface. By arranging movement of the tip of surface with which thisthis bendable extension so that it is initially inclined backwardly inthe manner just described, it will be clear that the radial clearance 15may be exceedingly small, and in the event any rubbing occurs, the pointof contact will always follow the :blade ii-11d hence, will cause .therubbed metal t0 flow 'iil One direction and tend to prevent vibrationwhen the rub takes place. Should any rub occur With-my Anovelib'lade,-it Wil-l thus bevseen that no serious consequences Will'resultand that,when access is had to the blading, the rubbed edgeJ portion may betrimmed andstraightened and the original clearance restored. Theextension l2, as will be noted from the .(lraxvings, extends'transversely .of the blade. When the edge coines 'into contact withininnte irregularities of ,the adjacent surface of .the casing 14, the,edge ,wll'yield or ,bend ,in 4the Alongiimdinal Adirection Aoftheblade. Thus the blade is A,not held .back and does not ,vibrate.

It will .be .readily app arent, therefore, that I have provided aturbine blade with means for preventing vibration due to rubbing.

While I have shown .my invention .in .bu-.t one forni, it Will beobvious,tofthoseslilled ,in the .art ,that .it is not so limited, .butis sus ceptibleof various changesand modifications y without departingfrom ,the spirit thereof,

,and l desire., therefore, that only such .limitaltions' shall .bepla-ced thereuponas v,are imposedyby .the prior .art or as are`specifically set orthin theqappendedlaims, .3.5 What I .claiin is; Y Y

1. Ina turbine, Athe combination of a rotor .and ,a cas-ing, ,a turbine,blade .carried by one of `said `parts with its ,tip .endradjraeent theotherofsaid parts, said tip `end ,being formed Y .40 with a relatively.thin extension bendable lon- `gitndinally .of the blade vand havingclose sealing clearance With said other part, .said extension being bentbackwardly with respecttothe direction odi rotationof theblld 4.5relative .to said othen-part.

2. rlhe combination defined in claim l, which .the bendable extension'is tormed .as `a continuation of one of the working faces Kof `theblade,

.50 In testimony WhereohlV have hereunto subscribed `lny naine .this27th day lof December,

`inertiaMIN v; panettone,

